1. Field of the Invention
The present invention relates to an apparatus and a method for detecting a frequency.
2. Description of the Related Art
A power meter is an apparatus capable of sensing an amount of consumed current using a current detection sensor and determining a total power amount by calculating the amount of consumed current by a predetermined voltage. Recently, interest in smart grids, next generation intelligent power networks capable of optimizing energy efficiency by bidirectionally exchanging real-time information between a power supplier and a power consumer through a combination of existing power networks and information technology devices, has increased. In accordance with a digitalization of power networks, consumers may check related information such as rates varying depending on a power supply and demand situation, or the like, and an energy source may be selected in real time, with a separate power management apparatus known as a smart meter.
In order to accurately determine the amount of power consumed in a power meter, a frequency of a signal input from a power line should be precisely detected. Therefore, in the related art such as the following Related Art Document, the frequency of a signal input from a power line has been detected using a zero crossing detection (ZCD) method, a method of detecting the frequency of the signal input from a power line from a crossing point of the input signal and a reference signal line having a zero level.
However, a power load having various forms may flow in power lines, such that an input signal may be introduced with a harmonic wave having a complicated form. As a result, the input signal may have a distorted form very different from that of an ideal sine wave. In this case, a plurality of zero crossing points may be present in a single period, according to conditions of a harmonic wave signal, such that precision in detecting the zero crossing point of ZCD may be decreased.
In order to solve the above-described problem, a method of measuring the frequency of a signal using a high frequency signal faster than a sampling frequency in an analog region, or over-sampling or interpolating in a digital region, has been used. However, even in such a case, since an operation clock frequency is increased, an amount of consumed power may be increased.